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Old Friday 29th July 2016, 13:25   #1
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Join Date: Jul 2008
Location: Tyresö
Posts: 710
extension tube lenght alters focal lenght?

at the moment I have approximatedly 10-11 cm extension tube lenght (80mm and pushed out a bit, as well as the camera mount adapter out a bit.

one of the photos below was taken at 300mm (zuiko 75-300) the other with the 600mm celestron 80ED, and sitting at the same spot. Sensor plane difference might have been a few centimeters, give or take. While upsizing the 300mm to match the other it took 255% - giving me approx 765mm.

Am I doing something wrong here? or can the small variance of a few centimeters me holding the camera give me so much of a diff? I mean, I sat on the same spot and just switched lens.
Attached Thumbnails
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ID:	593422  
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